1. Field of the Invention
The present invention is generally related to data and file storage systems and in particular to snapshot technology in file system backup.
2. Brief Description of Related Developments
Snapshot technology is currently supported in most File systems. Snapshots provide a stable and consistent image of a file system at a specific point in time. One of the major challenges with snapshot technology is the need to handle file system changes once the snapshot has been created. All file system changes must be included in the original file system, but they cannot appear in any corresponding snapshots. This is often done via Copy On Writes (COW) which requires additional IO and disk space to allow for file system changes while maintaining the snapshot image. One of the major consumers of snapshot technology is file system backup. Snapshots present a consistent file system for backup purposes, but often at a significant cost in terms of performance and disk space utilization. All changes require additional IO and disk space to maintain multiple versions of data that changed. This includes user data and metadata.
Current snapshot-backup processing requires COW activity for all file system changes for the duration of the entire backup process, which can be expensive in terms of I/O, CPU cycles, and disk space consumption.
It would be advantageous to be able to reduce COW activity during the snapshot backup process. It would also be advantageous to be able to minimize COW activity if backup prioritization were implemented. This would significantly reduce 10 and disk space consumption for active file systems. The more active the file system, the greater the benefit this would provide. Overall backup, file system and system performance would improve. These advantages also hold true for other applications as well, such as for example, on-line file system verification.